Network switch and components and method of operation

ABSTRACT

An apparatus is disclosed for transporting control information in a communications system. The apparatus comprises a network processor, a control point processor operatively coupled to the network processor, and a guided frame generated by the control point processor. The guided frame comprises a first section in which frame control information is placed and is used by the network processor to update at least one control register within the network processor; a second section carrying correlators assigned by the control point processor to correlate guided frame responses with their requests; a third section carrying one or a sequence of guided commands; and an End delimiter guided command.

This is a divisional application which claims priority of U.S. patentapplication Ser. No. 09/384,692, filed Aug. 27, 1999 now U.S. Pat. No.6,985,431.

RELATED APPLICATIONS

The interested reader is referred, for assistance in understanding theinventions here described, to the following prior disclosures which arerelevant to the description which follows and each of which is herebyincorporated by reference into this description as fully as if hererepeated in full:

U.S. Pat. No. 5,008,878, issued 16 Apr. 1991 for “High-Speed ModularSwitching Apparatus for Circuit and Packet Switched Traffic”;

U.S. Pat. No. 5,724,348, issued 3 Mar. 1998 for “EfficientHardware/Software Interface for a Data Switch”;

U.S. Pat. No. 5,787,430, issued 28 Jul. 1998 for “Variable Length DataSequence Backtracking a Trie Structure”;

U.S. Pat. No. 6,298,340, issued 2 Oct. 2001 for “System and Method andComputer Program for Filtering Using Tree Structure”; and

U.S. Pat. No. 6,222,380 issued 24 Apr. 2001 for “High SpeedParallel/Serial Link for Data Communication”.

BACKGROUND OF THE INVENTION

This invention relates to communication network apparatus such as isused to link together information handling systems or computers ofvarious types and capabilities and to components of such apparatus. Inparticular, this invention relates to scalable switch apparatus andcomponents useful in assembling such apparatus. This invention relatesto an improved and multi-functional interface device and the combinationof that device with other elements to provide a media speed networkswitch. The invention also relates to methods of operating suchapparatus which improve the data flow handling capability of networkswitches.

The description which follows presupposes knowledge of network datacommunications and switches and routers as used in such communicationsnetworks. In particular, the description presupposes familiarity withthe ISO model of network architecture which divides network operationinto layers. A typical architecture based upon the ISO model extendsfrom Layer 1 (also sometimes identified as “L1”) being the physicalpathway or media through which signals are passed upwards through Layers2, 3, 4 and so forth to Layer 7, the last mentioned being the layer ofapplications programming running on a computer system linked to thenetwork. In this document, mention of L1, L2 and so forth is intended torefer to the corresponding layer of a network architecture. Thedisclosure also presupposes a fundamental understanding of bit stringsknown as packets and frames in such network communication.

In today's networked world, bandwidth is a critical resource. Increasingnetwork traffic, driven by the Internet and other emerging applications,is straining the capacity of network infrastructures. To keep pace,organizations are looking for better technologies and methodologies tosupport and manage traffic growth and the convergence of voice withdata.

Today's dramatic increase in network traffic can be attributed to thepopularity of the Internet, a growing need for remote access toinformation, and emerging applications. The Internet alone, with itsexplosive growth in e-commerce, has placed a sometimes insupportableload on network backbones. It is also the single most important cause ofincreased data traffic volumes that exceed voice traffic for the firsttime. The growing demands of remote access applications, includinge-mail, database access, and file transfer, are further strainingnetworks.

The convergence of voice and data will play a large role in definingtomorrow's network environment. Currently, the transmission of data overInternet protocol (IP) networks is free. Because voice communicationswill naturally follow the path of lowest cost, voice will inevitablyconverge with data. Technologies such as Voice over IP (VoIP), Voiceover ATM (VoATM), and Voice over Frame Relay (VoFR) are cost-effectivealternatives in this changing market. However, to make migration tothese technologies possible, the industry has to ensure quality ofservice (QoS) for voice and determine how to charge for voice transferover data lines. The Telecommunications Deregulation Act of 1996 furthercomplicates this environment. This legislation will reinforce asymbiotic relationship between the voice protocol of choice, ATM, andthe data protocol of choice, IP.

Integrating legacy systems is also a crucial concern for organizationsas new products and capabilities become available. To preserve theirinvestments in existing equipment and software, organizations demandsolutions that allow them to migrate to new technologies withoutdisrupting their current operations.

Eliminating network bottlenecks continues to be a top priority forservice providers. Routers are often the source of these bottlenecks.However, network congestion in general is often misdiagnosed as abandwidth problem and is addressed by seeking higher-bandwidthsolutions. Today, manufacturers are recognizing this difficulty. Theyare turning to network processor technologies to manage bandwidthresources more efficiently and to provide the advanced data services, atwire speed, that are commonly found in routers and network applicationservers. These services include load balancing, QoS, gateways, firewalls, security, and web caching.

For remote access applications, performance, bandwidth-on-demand,security, and authentication rank as top priorities. The demand forintegration of QoS and CoS, integrated voice handling, and moresophisticated security solutions will also shape the designs of futureremote access network switches. Further, remote access will have toaccommodate an increasing number of physical mediums, such as ISDN, T1,E1, OC-3 through OC-48, cable, and xDSL modems.

Industry consultants have defined a network processor (herein alsomentioned as an “NP”) as a programmable communications integratedcircuit capable of performing one or more of the following functions:

-   -   Packet classification—identifying a packet based on known        characteristics, such as address or protocol    -   Packet modification—modifying the packet to comply with IP, ATM,        or other protocols (for example, updating the time-to-live field        in the header for IP)    -   Queue/policy management—reflects the design strategy for packet        queuing, de-queuing, and scheduling of packets for specific        applications    -   Packet forwarding—transmission and receipt of data over the        switch fabric and forwarding or routing the packet to the        appropriate address

Although this definition is an accurate description of the basicfeatures of early NPs, the full potential capabilities and benefits ofNPs are yet to be realized. Network processors can increase bandwidthand solve latency problems in a broad range of applications by allowingnetworking tasks previously handled in software to be executed inhardware. In addition, NPs can provide speed improvements througharchitectures, such as parallel distributed processing and pipelineprocessing designs. These capabilities can enable efficient searchengines, increase throughput, and provide rapid execution of complextasks.

Network processors are expected to become the fundamental networkbuilding block for networks in the same fashion that CPUs are for PCs.Typical capabilities offered by an NP are real-time processing,security, store and forward, switch fabric, and IP packet handling andlearning capabilities. NPs target ISO layer two through five and aredesigned to optimize network-specific tasks.

The processor-model NP incorporates multiple general purpose processorsand specialized logic. Suppliers are turning to this design to providescalable, flexible solutions that can accommodate change in a timely andcost-effective fashion. A processor-model NP allows distributedprocessing at lower levels of integration, providing higher throughput,flexibility and control. Programmability can enable easy migration tonew protocols and technologies, without requiring new ASIC designs. Withprocessor-model NPs, NEVs benefit from reduced non-refundableengineering costs and improved time-to-market.

BRIEF SUMMARY OF THE INVENTION

One purpose of this invention is to provide a scalable switcharchitecture for use in a data communication network which is capable ofsizing support capabilities to a range of potential demands whileimproving the speed of handling of data being transferred. This purposeis pursued by providing components, and assemblages of components, whichremove from the workload of processing units involved a greater amountof data handling than has been the case heretofore.

Another purpose is to provide an interface device or network processor(the terms being used interchangeably) which includes a plurality ofsub-assemblies integrated on a single substrate and coacting to providemedia rate switching of frames that include layer 2, layer 3, layer 4and layer 5. The interface device may be used as a standalone solutionproviding a first level of capability for a work group switch, aninterconnected solution providing a higher level of capability workgroup switch or scaled further upward in capability by cooperation witha switching fabric device.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the purposes of the invention having been stated, others willappear as the description proceeds, when taken in connection with theaccompanying drawings, in which:

FIG. 1 shows a block diagram for an interface device in accordance withthis invention.

FIG. 1A shows a block diagram for the MAC.

FIGS. 2A through 2D show the interface device interconnected with othercomponents in different system configurations.

FIG. 3 shows the flow and processing of an encapsulated guided frame.

FIG. 4 shows the flow and processing of an internal guided frame.

FIG. 5 shows generalized format for a Guided Cell.

FIG. 6 shows the format for Frame Control Information.

FIG. 7 shows the format for the Correlator.

FIG. 8 shows Command Control Information Format.

FIG. 9 shows Addressing Information Format.

FIG. 10 shows General Form of Structure Addressing.

FIG. 11 shows chart for Addressing, Island Encoding.

FIG. 12A shows a block diagram of the Embedded Processor Complex.

FIG. 12B shows a schematic of the Embedded Processors.

FIG. 12C shows a structure for a GxH Processor.

FIG. 13 shows a block diagram of the memory complex.

FIG. 14 shows a flowchart for the Fixed Match (FM) search algorithm.

FIG. 15 shows flows illustrating Data Structure without using a DirectTable and with using a Direct Table.

FIG. 16 shows a block diagram of a switching systems such as Prizma.

FIG. 17 shows a block diagram of a CP.

FIG. 18 shows a block diagram of the single chip Network Processorhighlighting function in the EDS-UP, EDS DOWN and the EPC.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

While the present inventions will be described more fully hereinafterwith reference to the accompanying drawings, in which preferredembodiments of the present inventions are shown, it is to be understoodat the outset of the description which follows that persons of skill inthe appropriate arts may modify the inventions here described whilestill achieving the favorable results of the inventions. Accordingly,the description which follows is to be understood as being a broad,teaching disclosure directed to persons of skill in the appropriatearts, and not as limiting upon the present inventions.

Apparatus disclosed here is scalable and capable of functioning tointerconnect desktop or workgroup switches, aggregate such switches intoa network backbone, and provide backbone switching services. Theapparatus can support Layer 2, Layer 3, and Layer 4+ forwarding inhardware. Certain forms of the apparatus are designed for desktop orworkgroup switch aggregation and while others are targeted as corebackbone switches.

The architecture used for the apparatus is based on an interface deviceor network processor hardware subsystem and a software library runningon a control point, all as more fully described elsewhere in thisdocument. The interface device or network processor subsystem is a highperformance frame forwarding engine designed for parsing and translationof L2, L3, and L4+ protocol headers. This allows protocols to beswitched at greater speeds using hardware. The interface device ornetwork processor subsystem provides a fast-path through the box whilethe software library and control point processor provide management androute discovery functions needed to maintain the fast-path. The controlpoint processor and the software library running thereon together definethe Control Point (CP) of the system. The CP is where the actualbridging and routing protocols such as Transparent Bridging and OSPF arerun. It can also be referred to as the slow-path of the system.

While the apparatus here disclosed supports multi-layer forwarding inhardware it can also operate as a L2 only switch and that is its defaultmode of operation in the simplest form disclosed. Each port will be putinto a single domain allowing any device to communicate with any otherdevice. The apparatus is configurable at L2 allowing systemadministrators the ability to configure features such as; grouping portsinto separate domains or trunks, configuring Virtual LAN (VLAN)segments, or filters to control broadcast and multicast traffic.

This scalable apparatus has many benefits. First, it allows the systemadministrator the ability to configure L3 forwarding and routing of IPand IPX traffic using the same hardware being used for L2 and at thesame speed. Second, it removes the need for using external routers tointerconnect campus buildings while increasing performance at the sametime. Third, it simplifies or combines the management of L2/L3 servicefor a building into a single point of control. Finally, it providesvalue added features with L4+ functions that allow system administratorsthe ability to assign different traffic classifications to supportmission critical applications and network dispatcher for load-balancingamong servers.

The apparatus is designed to be a modular unit using an interface deviceor network processor, a Control Point (CP), and an optional switchingfabric device as its fundamental building blocks. The interface devicepreferably provides L2/L3/L4+ fast-path forwarding services while the CPprovides the management and route discovery functions needed to maintainthe fast-path. The optional switching fabric device is used when morethan two interface device subsystems are tied together. The optionalswitching fabric device may be as disclosed in U.S. Pat. No. 5,008,878issued 16 Apr. 1991 for High Speed Modular Switching Apparatus forCircuit and Packet Switched Traffic mentioned hereinabove andincorporated herein by reference.

The apparatus is anticipated to be assembled using printed circuit boardelements also here mentioned as “blades”. The printed circuit boardelements have circuit elements mounted thereon and are received inconnectors provided in apparatus housings. Similar devices are also knowas “option cards”. The apparatus contemplates that blades can beexchanged among varying chassis or housings, provided that appropriateconnectors and backplane electrical connections are provided. The basiccomponent found on all blades is a carrier subsystem. Starting with thecarrier subsystem, three types of blades can be produced. The first typeis a CP only Blade, which consists of a carrier subsystem and a CPsubsystem. The primary use of a CP only blade is for a product whereredundancy is the primary concern. The second type is a CP+Media Blade,which consists of a carrier subsystem, a CP subsystem, and 1-to-3 mediasubsystems. The primary use of a CP+Media blade is a product where portdensity is deemed more important than redundancy. The third type is aMedia Blade, which consists of a carrier subsystem and 1-to-4 mediasubsystems. The media blades can be used in any chassis and the type ofmedia subsystem used is configurable.

Blade management will involve fault detection, power management, newdevice detection, initialization, and configuration. This managementwill be done using various registers, I/O signals, and a guided cellinterface that is used to communicate between the CP and carriersubsystems. However, unlike the chassis there does exist programmabledevices and memory on all blades. The amount of programmability dependson the type of blade. When the CP subsystem exists on a blade both theCP and carrier subsystems are programmable. The media subsystems arealso programmable but only indirectly through the carrier subsystem.

In higher capability products there also exists a Switch Blade whichcontains the switching fabric device subsystem. The management of thisblade will involve fault detection, power management, new devicedetection, and initialization. This management will be done usingvarious registers and I/O signals that will be mapped into the CPsubsystem.

In its simplest form, a switch apparatus contemplated by this inventionhas a control point processor; and an interface device operativelyconnected to the control point processor. Preferably and as heredisclosed, the interface device (also known as a network processor) is aunitary Very Large Scale Integrated (VLSI) circuit device or chip whichhas a semiconductor substrate; a plurality of interface processorsformed on the substrate; internal instruction memory formed on saidsubstrate and storing instructions accessibly to the interfaceprocessors; internal data memory formed on the substrate and storingdata passing through the device accessibly to the interface processors;and a plurality of input/output ports. The interface processors are alsosometimes herein identified as picoprocessors or processing units. Theports provided include at least one ports connecting the internal datamemory with external data memory and at least two other ports exchangingdata passing through the interface device with an external network underthe direction of the interface processors. The control point cooperateswith the interface device by loading into the instruction memoryinstructions to be executed by the interface processors in directing theexchange of data between the data exchange input/output ports and theflow of data through the data memory.

The network processor here disclosed is deemed inventive apart from theswitch assemblies into which it is incorporated. Further, the networkprocessor here disclosed is deemed to have within its elements heredescribed other and further inventions not here fully discussed.

FIG. 1 shows a block diagram for the interface device chip that includessubstrate 10 and a plurality of sub-assemblies integrated on thesubstrate. The sub-assemblies are arranged into an Upside configurationand a Downside configuration. As used herein, “Upside” refers to dataflows inbound from a network to the apparatus here disclosed, while“Downside” refers to data outbound from the apparatus to a networkserviced by the apparatus. The data flow follows the respectiveconfigurations. As a consequence, there is an Upside data flow and aDownside data flow. The sub-assemblies in the Upside includeEnqueue-Dequeue-Scheduling UP (EDS-UP) logic 16, multiplexed MAC's-UP(PPM-UP) 14, Switch Data Mover-UP (SDM-UP) 18, System Interface (SIF)20, Data Align Serial Link A (DASLA) 22, and Data Align Serial Link B(DASLB) 24. A data align serial link is more fully described incopending U.S. patent application Ser. No. 09/330,968 filed 11 Jun. 1999and entitled “High Speed Parallel/Serial Link for Data Communication”mentioned hereinabove and incorporated by reference hereinto. While thepreferred form of the apparatus of this invention here disclosed uses aDASL link, the present invention contemplates that other forms of linksmay be employed to achieve relatively high data flow rates, particularlywhere the data flows are restricted to being within the VLSI structure.

The sub-assemblies in the downside include DASL-A 26, DASL-B 28, SIF 30,SDM-DN 32, EDS-DN 34, and PPM-DN 36. The chip also includes a pluralityof internal S-RAM's, Traffic Mgt Scheduler 40, and Embedded ProcessorComplex (EPC) 12. An interface device 38 is coupled by respective DMUBusses to PMM 14 and 36. The interface 38 could be any suitable L1circuitry, such as ethernet Physical (ENET PHY), ATM Framer, etc. Thetype of interface is dictated in part by the network media to which thechip is connected. A plurality of external D-RAM's and S-RAM areavailable for use by the chip.

While here particularly disclosed for networks in which the general dataflow outside the relevant switching and routing devices is passedthrough electrical conductors such as wires and cables installed inbuildings, the present invention contemplates that the network switchesand components thereof here disclosed may be used in a wirelessenvironment as well. By way of an illustrative example, the media accesscontrol (MAC) elements here described may be replaced by suitable radiofrequency elements, possibly using known Silicon Germanium technology,which would result in a capability to link the elements here describeddirectly to a wireless network. Where such technology is appropriatelyemployed, the radio frequency elements can, by person of appropriateskill in the applicable arts, be integrated into the VLSI structureshere disclosed. Alternatively, radio frequency or otherwise wirelessresponse devices such as infrared responsive devices can be mounted on ablade with other elements here disclosed to achieve a switch apparatususeful with wireless network systems.

The arrows show the general flow of data within the Interface device.Frames received from an Ethernet MAC are placed in internal Data Storebuffers by the EDS-UP. These frames are identified as either normal DataFrames or system control Guided Frames and enqueued to the EPC (FIG. 1).The EPC contains N protocol processors capable of working on up to Nframes in parallel (N>1). In an embodiment of ten protocol processor(FIG. 12B), two of the ten protocol processors are specialized; one forhandling Guided Frames (the Generic Central Handler or GCH) and one forbuilding Lookup Data in Control Memory (the Generic Tree Handler orGTH). As shown in FIG. 12A, the EPC also contains a dispatcher whichmatches new frames with idle processors, a completion unit whichmaintains frame sequence, a Common Instruction memory shared by all tenprocessors, a Classifier Hardware Assist which determines frameclassification and coprocessor which helps determine the startinginstruction address of the frame, Ingress and Egress Data Storeinterfaces which control read and write operations of frame buffers, aControl Memory Arbiter which allows the ten processors to share ControlMemory, a Web Control, Arbiter and interface that allows debug access tointernal Interface device data structures, as well as other hardwareconstructs.

Guided Frames are sent by the dispatcher to the GCH processor as itbecomes available. Operations encoded in the Guided Frame are executed,such as register writes, counter reads, Ethernet MAC configurationchanges, and so on. Lookup table alterations, such as adding MAC or IPentries, are passed on to the Lookup Data processor for Control Memoryoperations, such as memory reads and writes. Some commands, such as MIBcounter reads, require a response frame to be built and forwarded to theappropriate port on the appropriate Interface device. In some cases, theGuided Frame is encoded for the Egress side of Interface device. Theseframes are forwarded to the Egress side of the Interface device beingqueried, which then executes the encoded operations and builds anyappropriate response frame.

Data frames are dispatched to the next available protocol processor forperforming frame lookups. Frame data are passed to the protocolprocessor along with results from the Classifier Hardware Assist (CHA)Engine. The CHA parses IP or IPX. The results determine the Tree Searchalgorithm and starting Common Instruction Address (CIA). Tree Searchalgorithms supported included Fixed Match Trees (fixed size patternsrequiring exact match, such as Layer 2 Ethernet MAC tables), Longestprefix Match Trees (variable length patterns requiring variable lengthmatches, such as subnet IP forwarding) and Software Managed Trees (twopatterns defining either a range or a bit mask set, such as used forfilter rules).

Lookup is performed with the aid of the Tree Search Engine (TSE)Coprocessor, which is a part of each protocol processor. The TSECoprocessor performs Control memory accesses, freeing the protocolprocessor to continue execution. Control memory stores all tables,counters, and other data needed by the picocode. Control memoryoperations are managed by the Control memory Arbiter, which arbitratesmemory access among the ten processor complexes.

Frame data are accessed through the Data Store Coprocessor. The DataStore Coprocessor contains a primary data buffer (holding up to eight 16byte segments of frame data), a scratch pad data buffer (also holding upto eight 16-byte segments of frame data) and some control registers forData Store operations. Once a match is found, Ingress frame alterationsmay include a VLAN header insertion or overlay. This alteration is notperformed by the interface device processor complex, but rather hardwareflags are derived and other Ingress Switch Interface hardware performsthe alterations. Other frame alterations can be accomplished by thepicocode and the Data Store Coprocessor by modifying the frame contentsheld in the Ingress Data Store.

Other data are gathered and used to build Switch Headers and FrameHeaders prior to sending frames to the switch fabric device. Controldata include switch information, such as the destination blade of theframe, as well as information for the Egress Interface device, helpingit expedite frame lookup of destination ports, multicast or unicastoperations, and Egress Frame alterations.

Upon completion, the Enqueue Coprocessor builds the necessary formatsfor enqueuing the frame to the switch fabric and sends them to theCompletion Unit. The Completion Unit guarantees frame order from the tenprotocol processors to the switch fabric queues. Frames from the switchfabric queues are segmented into 64 byte cells with Frame Header bytesand Switch Header bytes inserted as they are transmitted to the Prizma-ESwitch.

Frames received from the switch fabric are placed in Egress Data Store(Egress DS) buffers by an Egress EDS (34) and enqueued to the EPC. Aportion of the frame is sent by the dispatcher to an idle protocolprocessor for performing frame lookups. Frame data are dispatched to theprotocol processor along with data from the Classifier Hardware Assist.The Classifier Hardware Assist uses frame control data created by theIngress Interface device to help determine the beginning CodeInstruction Address (CIA).

Egress Tree Searches support the same algorithms as supported forIngress Searches. Lookup is performed with the TSE Coprocessor, freeingthe protocol processor to continue execution. All Control memoryoperations are managed by the Control memory Arbiter, which allocatesmemory access among the ten processor complexes.

Egress frame data are accessed through the Data Store Coprocessor. TheData Store Coprocessor contains a primary data buffer (holding up toeight 16-byte segments of frame data), a scratch pad data buffer (alsoholding up to eight 16-byte segments of frame data) and some controlregisters for Data Store operations. The result of a successful lookupcontains forwarding information and, in some cases, frame alterationinformation. Frame alterations can include VLAN header deletion, Time toLive increment (IPX) or decrement (IP), IP Header Checksumrecalculation, Ethernet frame CRC overlay or insertion and MAC DA/SAoverlay or insertion. IP Header checksums are prepared by the ChecksumCoprocessor. Alterations are not performed by the Interface deviceProcessor Complex, but rather hardware flags are created and PMM Egresshardware performs the alterations. Upon completion, the EnqueueCoprocessor is used to help build the necessary formats for enqueuingthe frame in the EDS Egress queues and sending them to the CompletionUnit. The Completion Unit guarantees frame order from the ten protocolprocessors to the EDS Egress queues feeding the egress Ethernet MACs 36.

The completed frames are finally sent by PMM Egress hardware to theEthernet MACs and out the Ethernet ports.

An internal bus, referred to as the Web, allows access to internalregisters, counters and memory. The Web also includes an externalinterface to control instruction step and interrupt control fordebugging and diagnostics.

Tree Search Engine coprocessor provides memory range checking, illegalmemory access notification and performs tree search instructions (suchas memory read, write or read-add-write) operating in parallel withprotocol processor execution.

Common Instruction Memory consists of one 1024×128 RAM and two sets ofDual 512×128 RAM. Each set of Dual RAMs provides two copies of the samepicocode, allowing processors independent access to instructions withinthe same address range. Each 128-bit word includes four 32-bitinstructions, providing a total range of 8192 instructions.

The Dispatcher controls the passing of frames to the ten protocolprocessors and manages interrupts and timers.

The Completion Unit guarantees frame order from the processor complex tothe switch fabric and target port queues. A rich instruction setincludes conditional execution, packing (for input hash keys),conditional branching, signed and unsigned operations, counts of leadingzeros and more.

The Classifier Hardware Assist engine parses each frames layer 2 andlayer 3 protocol header and provides this information with frames asthey are dispatched to the protocol processors.

The Control memory Arbiter controls processor access to both internaland external memory.

External Control memory options include 5 to 7 DDR DRAM subsystems eachsupporting a pair of 2M×16 bit×4 bank or a pair of 4M×16 bit×4 bank DDRDRAMs. The DDR DRAM interface runs at a 133 MHZ clock rate and a 266 MHZdata strobe supporting configurable CAS latency and drive strength. Anoptional 133 MHZ ZBT SRAM can be added in either a 128K×36, 2×256K×18 or2×512K×18 configuration.

Egress frames may be stored in either one External Data Buffer (e.g.DS0) or two External Data Buffers (DS0 and DS1). Each Buffer can becomprised of a pair of 2M×16 bit×4 bank DDR DRAM (storing up to 256K64-byte frames) or a pair of 4M×16 bit×4 bank DDR DRAM (storing up to512K 64-byte frames). Choose the single External Data Buffer (e.g. DS0)for 2.28 Mbps or add the second Buffer (e.g. DS1) to support 4.57 Mbpslayer 2 and layer 3 switching. Adding the second Buffer improvesperformance, but it does not increase frame capacity. The External DataBuffer interface runs at a 133 MHZ clock rate with a 266 MHZ data strobeand supports configurable CAS latency and drive strength.

Internal Control memory includes two 512×128 bit RAMs, two 1024×36 bitRAMs and one 1024×64 bit RAM.

Internal Data storage provides buffering for up to 2048 64-byte framesin the Ingress direction (UP).

Fixed Frame alterations include VLAN tag insertions in the Ingressdirection and VLAN tag deletions, Time To Live increment/decrement (IP,IPx), Ethernet CRC overlay/insert and MAC DA/SA overlay/insert in theEgress (DOWN) direction.

Port mirroring allows one receive port and one transmit port to becopied to a system designated observation port without using protocolprocessor resources. Mirrored Interface device ports are configured toadd frame and switch control data. A separate data path allows directframe enqueuing to the Ingress Switch interface.

The interface device integrates four Ethernet macros. Each macro can beindividually configured to operate in either 1 Gigabit or 10/100 FastEthernet modes. Each Ethernet macro supports the following:

Up to ten 10/100 Mbps MACs or one 1000 Mbps MACs for each of fourmacros.

FIG. 1A shows a block diagram of the MAC core. Each macro includes threeEthernet Core designs; to wit, the multiport 10/100 Mbps MAC Core(Fenet), the 1000 Mbps MAC core (Genet) and the 100 Mbps Physical CodingSublayer Core (PCS).

Multi-Port Ethernet 10/100 MAC Features:

-   -   Supports ten Serial Medium Independent Interfaces to the        physical layer    -   Capable of handling ten ports of 10 Mbps or 100 Mbps media        speeds, any speed mix    -   A single MAC services all ten ports with a Time Division        Multiplex interface    -   Supports Full/Half duplex operations at media speed on all ports    -   Supports IEEE 802.3 Binary Exponential Backoff        1000 Mbps Ethernet MAC Core Features:

Supports Gigabit Medium Independent Interface (GMII) to the physical PCSlayer or directly to the physical layer

With the PCS Core, supports a complete TBI (8b/10b) solution

Supports Full duplex Point-to-Point connections at media speed

Supports the IBM PCS Core valid byte signalling

1000 Mbps Ethernet Physical Coding Sublayer Core Features:

Performs 8b/10b encoding and decoding

Supports the PMA (10 bit) Service Interface as defined in IEEE 802.3z,this interface attaches to any PMA that is compliant with IEEE 802.3z

Synchronizes data received from the PMA (two phase clock) with the MAC(single phase) clock

Supports Auto-Negotiation including two next pages

Converts from a two phase clock system defined in the standards to asingle phase clock

Provides a signal to the MAC indicating those clock cycles that containnew data

Checks the received code groups (10 bits) for COMMA's and establishesword sync

Calculates and checks the 8b/10b running disparity

FIGS. 2A-2D show different configurations for the Interface device Chip.The configurations are facilitated by DASL and connection to a switchingfabric device. Each DASL includes two channels; namely, a transmitchannel and a receiver channel.

FIG. 2A shows a wrap configuration for a single Interface device. Inthis configuration, the transmit channel is wrapped to the receivechannel.

FIG. 2B shows the configuration in which two Interface device Chips areconnected. Each Interface device Chips is provided with at least twoDASLs. In this configuration, the channels on one DASL on one chip areoperatively connected to the channels of a matching DASL on the otherchip. The other DASL channel on each chip is wrapped.

FIG. 2C shows the configuration in which multiple Interface devices areconnected to a switch fabric. The double headed arrows indicatetransmission in both direction.

FIG. 2D shows the configuration in which a Main switch and a Backupswitch are connected to Multiple Interface devices. If the main switchgoes down, the backup is available for use.

A Control Point (CP) includes a System Processor that is connected toeach of the configuration. The system processor at the CP, among otherthings, provides initialization and configuration services to the chip.The CP may be located in any of three locations: in the interface devicechip; on the blade on which the chip is mounted or external to theblade. If external to the blade, the CP may be remote; that is, housedelsewhere and communicating by the network to which the interface deviceand CP are attached. The elements of a CP are shown in FIG. 17 andinclude memory elements (cache, flash and SDRAM), a memory controller, aPCI bus, and connectors for a backplane and for L1 network media.

FIG. 18 shows the single chip Network Processor and the functionsprovided by the EDS-UP, the traffic Management (MGT) Scheduler and theEDS-DOWN (DN). The U-shaped icons represent queues and the ControlBlocks (CB) that keeps track of the contents in the queues arerepresented by rectangular icons.

A description of the elements, their respective functions andinteraction follows.

PMM: This is the part of the Network Processors that contains the MACs(FEnet, POS, GEnet) and attaches to the external PHY devices.

UP-PMM: This logic takes bytes from the PHYs, and formats it into FISH(16 bytes) to pass on to the UP-EDS. There are 4 DMUs within the PMM,each capable of working with 1 GEnet or 10 FEnet devices.

UP-EDS: This logic takes the fish from UP-PMM and stores them into theUP-Data Store (internal RAM). It is capable of working on 40 frames atonce, and after the appropriate number of bytes are received, it willenqueue the frame to the EPC. When the EPC is finished with the frame,the UP-EDS will enqueue the frame into the appropriate Target Port Queueand start sending the frame to the UP-SDM. The UP-EDS is responsible forall buffer and frame management and returns the buffers/frames back tofree pools when the transfer to UP-SDM is complete.EPC: This logic contains the picoprocessors and (could) contain theembedded PowerPC. This logic is capable of looking at the frame headerand deciding what to do with the frame (forward, modify, filter, etc.).The EPC has access to several lookup tables, and hardware assists toallow the picoprocessors to keep up with the high-bandwidth requirementsof the Network Processor.UP-SDM: This logic takes the frames, and formats them into PRIZMA cellsfor transmission to the switch fabric. This logic is also capable ofinserting the VLAN header into the frame.UP-SIF: This logic contains the UP-DASL macros and attaches to theexternal switch I/Os.DN-SIF: This logic contains the DN-DASL macros and receives PRIZMA cellsfrom the external I/Os.DN-SDM: This logic receives the PRIZMA cells and preprocesses them forhelp in frame reassembly.DN-EDS: This logic takes each cell and assembles them back into frames.The cell is stored into external Data Store, and buffers are linkedtogether to make frames. When the entire frame is received, the framewill be enqueued to the EPC. After EPC is finished with the frame, it isenqueued to the Scheduler (if present) or the Target Port Queues. DN-EDSthen sends the frames to the appropriate port by sending the frame, anyalteration information, and some control information to the DN-PMM.DN-PMM: Takes the information from DN-EDS and formats the frame intoEthernet, POS, etc. and sends the frame to the external PHY.SPM: This logic is used to allow the Network Processor to interface toexternal devices (PHYs, LEDs, FLASH, etc) but only requires 3 I/Os. TheNetwork Processor uses a serial interface to communicate to SPM and thenSPM preforms the necessary functions to manage these external devices.UP-SIDE Flow

-   1) Frame arrive at PHY-   2) Bytes are received by UP-PMM-   3) UP-PMM sends FISH over to UP-EDS (Fish means a portion of a    frame)-   4) UP-EDS stores FISH into UP-DS-   5) UP-EDS sends header over to EPC-   6) EPC processes header and sends enqueue information back to UP-EDS-   7) UP-EDS continues to receive the remainder of frame from UP-PMM-   8) UP-EDS sends information to UP-SDM when appropriate data is ready    to send to switch-   9) UP-SDM reads frame data and formats it into PRIZMA cells-   10) UP-SDM sends cells to UP-SIF-   11) UP-SIF transfers the cells over the DASL serial links to PRIZMA-   12) UP-EDS frees up buffers/frames when all the data has been taken    DN-SIDE Flow-   1) DN-SIF receives PRIZMA cells-   2) DN-SDM stores cells and preprocesses them for reassembly    information-   3) DN-EDS receives the cell data and reassembly information and    links the cell into a new frame on down side-   4) DN-EDS stores the cell into DN-DS-   5) DN-EDS enqueues the frame to EPC when all of the data have been    received-   6) EPC processes the header and sends enqueue information back to    DN-EDS-   7) DN-EDS enqueues the frame into a scheduler queue (if present) or    a Target Port Queue-   8) DN-EDS services the queues and sends frame information into the    PCB-   9) DN-EDS uses the PCB to “unravel” the frame and reads the    appropriate data and sends that data to DN-PMM-   10) DN-PMM formats the data (with alteration if requested) and sends    the frame to the external PHY-   11) DN-PMM informs DN-EDS when buffers are no longer needed and    DN-EDS frees these resources    FRAME Control Flow-   1) Header is sent to EPC from UP-DS or DN-DS-   2) EPC looks up header information in lookup tables and receives    frame enqueue information-   3) EPC sends the enqueue information back to the EDS and the frame    is enqueued to the appropriate queue-   4) Cell Headers and Frame Headers are sent along with the frame data    to aid in reassembly and frame forwarding    CP Control Flow-   1) Control Point formats a Guided Frame and sends it to the Network    Processor-   2) The Network Processor enqueues the Guided Frame to the GCH    picoprocessor-   3) The GCH processes the Guided Frame and reads or writes the    requested areas of Rainier-   4) The GCH passes any Table update requests over to the GTH-   5) The GTH updates the appropriate table with information from    Guided Frame-   6) An acknowledgement Guided Frame is sent back to CP    Network Processor Control Flow-   1) A Picoprocessor can build a Guided Frame to send information to    another Rainier or the Control Point-   2) The Guided Frame is sent to the appropriate location for    processing

A single Interface device provides media speed switching for up to 40Fast Ethernet Ports (FIG. 2A). 80 Fast Ethernet Ports are supported whentwo Interface devices are interconnected using IBM's Data AlignedSynchronous Link (DASL) technology (FIG. 2B). Each DASL differentialpair carries 440 Mbps of data. Two sets of eight pairs provide a 3.5Gbps duplex connection (8 times 440 Mbps in each direction). As shown inFIGS. 2C and 2D, larger systems can be built by interconnecting multipleInterface devices to a switch such as IBM's Prizma-E switch. TheInterface device provides two of the 3.5 Gbps duplex DASL connections,one primary and one secondary, which can be used to provide awrap-backpath for local frame traffic (when two Interface devices aredirectly connected, FIG. 2B) or a connection to a redundant switchfabric (FIG. 2D, Backup Sw.). In view of the above, the single NetworkProcessor Chip is scaleable in that one chip can be used to provide alow end system (having relatively low port density—say 40) to high endsystem (having relatively high port density, say 80−n ports).

One Interface device in the system is connected to the system processorvia one of up to ten 10/100 Mbps Fast Ethernet ports or a single 1000Mbps Ethernet port. The Ethernet configuration to the system processoris placed in an EEPROM attached to the Interface device and loadedduring initialization. The system processor communicates with allInterface devices in a system (see FIG. 2) by building special GuidedFrames encapsulated, for example, as ethernet frames or other mediainterfaces. The encapsulated Guided Frames are forwarded across the DASLlink to other devices allowing all of the Interface devices in thesystem to be controlled from a single point.

Guided Frames are used to communicate control information between theControl Point (CP) and the Embedded Processor Complex and within theinterface device. A prior disclosure of Guided Cells which willelucidate the discussion here is found in U.S. Pat. No. 5,724,348 issued3 Mar. 1998 for Efficient Hardware/Software Interface for a Data Switch”mentioned hereinabove and incorporated hereinto by reference.

For Guided Frame traffic that originates at the CP, the CP constructsthe Guided Frame in data buffers in its local memory. The CP's DeviceDriver sends the Guided Frame to one of the media interfaces of theNetwork Processor. Media Access Control (MAC) hardware recovers theGuided Frame and stores it in its internal data store (U_DS) memory. TheGuided Frame is routed to the appropriate blade, processed, and routedback to the CP as required. Guided Frames passing between an external CPand the interface device are encapsulated to adapt to the protocol ofthe external network. As a consequence, if the external network includesethernet, the Guided Frames are encapsulated as ethernet frames and soforth.

Ethernet encapsulation provides a means of transport for Guided Trafficbetween the CP and the Interface device. The Ethernet MAC (Enet MAC) ofthe Interface device does not analyze the Destination Address (DA) orSource Address (SA) when receiving frames. This analysis is performed bythe EPC picocode. Guided Traffic presumes that the Interface device hasnot been configured and the DA and SA cannot be analysed by the EPCpicocode. Therefore, these frames are inherently self-routing. The EnetMAC does, however, analyse the Ethernet Type field to distinguish GuidedTraffic from Data Traffic. The value of this Ethernet Type value of theGuided Frame must match the value loaded into the E_Type_C Register.This register is loaded from Flash Memory by the Interface device's bootpicocode.

The CP constructs the Guided Frame in data buffers in its local memory.The contents of a 32 bit register in the CP processor are stored in bigendian format in the local memory as shown in FIG. 3. Having constructedthe Guided Frame, the CP'S Device Driver sends an Ethernet framecontaining a DA for specific Guided Cell Handler (GCH), an SAcorresponding to the global MAC address for the CP or the MAC addressfor specific interface, a special Ethernet Type field that indicates aGuided Frame, and the Guided Frame Data. All Ethernet frames arriving onthe port are received and analyzed by Enet MAC. For frames with anEthernet Type value matching the contents of the E_Type_C Register, theEnet MAC strips off the DA, SA and Ethernet Type fields and stores theGuided Frame data into the U_DS memory. Bytes are collected by the EnetMAC one at a time into a block of 16 bytes called a Fish. These bytesare stored in big endian format with the first byte of the Guided Framestored in the most significant byte location of the Fish (Byte 0).Succeeding bytes are stored in successive byte locations within the Fish(Byte 1, Byte 2, . . . , Byte 15). These 16 bytes are then stored in aBuffer in the U_DS beginning at the Fish 0 location. Succeeding Fishesare stored in successive Fish locations within the Buffer (Fish 1, Fish2, Fish 3, etc.). Additional Buffers are obtained from a free pool asrequired to store the remainder of the Guided Frame.

The flow of guided traffic within the interface device 10 is shown inFIG. 4. The Enet MAC function of the Interface device examines the frameheader information and determines that the frame is a Guided Frame. TheEnet MAC removes the frame header from the Guided Frame and buffers theremainder of its contents in Interface device's internal U_DS memory.The Enet MAC indicates that the frame is to be enqueued to the GeneralControl (GC) Queue for processing by the GCH. When the end of the GuidedFrame has been reached, the Enqueue, Dequeue, and Schedule (EDS) logicenqueues the frame into the GC Queue.

The GCH picocode on the blade locally attached to the CP examines theFrame Control Information (see FIG. 6) to determine whether the GuidedFrame is intended for other blades in the system and whether the GuidedFrame is to be executed on the down side of the Interface device. If theframe is intended for blades other than or in addition to the locallyattached blade, the GCH picocode updates the TB value in the FrameControl Block (FCB) with the TB value from the Guided Frame's FrameControl information and instructs the EDS to enqueue the frame in themulticast Target Blade Start of Frame (TB_SOF) Queue. For performancereasons, all Guided Traffic is enqueued to the multicast TB_SOF queueindependent of the number of destination blades indicated.

If the frame is intended for only the locally attached blade, the GCHpicocode examines the up/down field of the Frame Control information todetermine whether the Guided Frame is to be executed on the up or downside of the Interface device (see FIG. 6). If the Guided Frame is to beexecuted on the down side of the Interface device, the GCH picocodeupdates the TB value in the FCB with the TB value from the GuidedFrame's Frame Control information and instructs the EDS to enqueue theframe in the multicast Target Blade Start of Frame (TB_SOF) Queue. Ifthe Frame Control information indicates that the Guided Frame is to beexecuted on the up side, the GCH picocode analyzes the Guided Frame andperforms the operations indicated by the Guided Commands it contains.

Prior to processing of Guided Commands, the picocode checks the value ofthe ack/ noack field of the Frame Control information. If this value is‘0’b, then the Guided Frame is discarded following processing. Guidedread commands shall not be of this category.

If the value of the ack/ noack field is ‘1’b, and the value of theearly/late field is ‘1’b, then prior to processing any of the GuidedCommands in the Guided Frame, the picocode constructs an Early AckGuided Frame with the value of the TB field of the Frame Control equalto the contents of the Early_Ack Guided Frame with the value of the TBfield of the Frame Control equal to the contents of the My_TB Register.The picocode routes the Early Ack Guided Frame back to the CP byupdating the TB value in the frame's FCB with the value contained in theTB field of the LAN Control Point Address (LAN_CP_Addr) Register andinstructing the EDS to enqueue the frame in the multicast TB_SOF Queue.The picocode then processes the Guided Commands of the Guided Frame anddiscards the Guided Frame. Guided read commands shall not be of thiscategory.

If, on the other hand, the value of the ack/ noack field is ‘1’b and thevalue of the early/late field is ‘0’b, the picocode changes the resp/req field of the Frame Control information to ‘1’b to indicate a GuidedFrame response, replaces the TB field with the contents of the My_TBRegister, and processes each Guided Command within the Guided Frame.During the course of processing a Guided Command, the picocode updatesthe Completion Code field of the next Guided Command with the completionstatus code value for the current Guided Command. The picocode routesthe response back to the source by updating the TB value in the (FCB)with the value corresponding to the Source Blade (LAN_CP_Addr Registervalue for CP) and instructing the EDS to enqueue the frame in themulticast TB_SOF Queue.

Frames residing in the TB_SOF Queue are scheduled for forwarding by theEDS. The Switch Data Mover (SDM) builds the switching fabric Cell Headerand Interface device Frame Header from the information contained in theFCB. These cells pass through the switching fabric device and arrive atthe target blade where the cells are reassembled into a frame in theD-DS memory. The SDM of the down side recognizes that the frame is aGuided Frame and signals the EDS to enqueue it in the GC Queue.

Pressure from the GC Queue or the GT Queue stimulates the picocode toaccess and analyse the Guided Frames. All Guided Frames arriving on thedown side are initially enqueued in the GC Queue. The gth/ gch value ofthe Frame Control Information for these frames is examined by GCHpicocode. If the gth/ gch value is ‘0’b, the Guided Frame is enqueued inthe GT Queue. Otherwise, the GCH picocode examines the resp/ req fieldof the Frame Control information to determine if the Guided Frame hasalready been executed. If the resp/ req has a value of ‘1’b, then theGuided Frame has already been executed and is routed to the CP. Targetport values corresponding to CP connections are maintained by EPCpicocode. Frames from these Target Port queues are transmitted from theInterface device back to the CP.

If the resp/ req field has a value of ‘0’b, then the blade may be localor remote with respect to the CP. This is resolved by comparing thevalue of the TB field of the LAN_CP_Addr Register with the contents ofthe My Target Blade (My_TB) Register. If they match, then the blade islocal to the CP, otherwise, the blade is remote form the CP. In eithercase, the picocode examines the up/down value of the Frame ControlInformation. If up/ down is equal to ‘1’b, then the frame is enqueued inthe Wrap TP queue for forwarding to the U_DS and processing by the GCHon the up side. Otherwise, the picocode (GCH or Gth) performs theoperations indicted by the Guided Commands contained in the GuidedFrame. Prior to processing of the Guided Commands, the picocode checksthe value of the ack/ noack field of the Frame Control information. Ifthis value is ‘0’b, then the Guided Frame is discarded followingprocessing. Guided read commands shall not be of this category.

If the value of the ack/ noack field is ‘1’b and the value of the early/late field is ‘1’b, then prior to processing any of the Guided Commandsin the Guided Frame, the picocode constructs an Early Ack Guided Framewith the value of the TB field of the Frame Control information equal tothe contents of the My_TB Register. If the bade is remote from the CP,the picocode routes the Early Ack Guided Frame to the Wrap Port.Otherwise, the blade is local to the CP and the frame is routed to thePort Queue corresponding to the CP. The picocode processes the GuidedCommands while either the Wrap Port moves the Early Ack Guided Framefrom the D_DS to the U_DS and enqueues the frame in the GC Queue on theup side or the frame is transmitted from the Port Queue back to the CP.For frames wrapped back to the U_DS, the GCH picocode again sees thisframe, but the resp/ req field will have a value of ‘1’b. The GCHpicocode routes the frame back to the CP by updating the TB field in theFCB with the value contained in the TB field of the LAN_CP_Addr Registerand instructing the EDS to enqueue the frame in the multicast TB_SOFQueue. Frames residing in the TB_SOF Queue are scheduled for forwardingby the EDS. The SDM builds the Prizma Cell Header and Interface deviceFrame header from information contained in the FCB. Cells from thisframe pass through Prizma and are reassembled into a frame on the CP'slocal blade. The SDM of the down side recognizes that the frame is aGuided Frame and signals the EDS to enqueue it in the GC Queue. Thistime when the GCH picocode analyzes the frame, the resp/req field has avalue of ‘1’b. This implies that this blade is locally attached to theCP and the Guided Frame is routed to the Port Queue corresponding to theCP. Frames from this queue are transmitted from Interface device back tothe CP.

If, on the other hand, the value of the ack/ noack field is ‘1’b and thevalue of the early/ late field is ‘0’b, the picocode changes theresp/req field to ‘1’b to indicate a Guided Frame response, replaces theTB field with the contents of the My_TB Register, and then processeseach Guided Command within the Guided Frame. During the course ofprocessing a Guided Command, the picocode updates the Completion Codefield of the next Guided Command with the completion status code valuefor the current Guided Command. If the blade is remote from the CP, thenthe picocode routes the Guided Frame to the Wrap Port. Otherwise, theblade is local to the CP and the frame is routed to the Port Queuecorresponding to the CP. Either the Wrap Port moves the Guided Framefrom the D_DS to the U_DS and enqueues the frame in the GC Queue on theup side or the frame is transmitted form the Port Queue back to the CP.For frames wrapped back to the U_DS, the GCH picocode again sees thisframe, but the resp/ req field will have a value of ‘1’b. The GCHpicocode routes the frame back to the CP by updating the TB field in theFCB with the value contained in the TB field of the LAN_CP_Addr Registerand instructing the EDS to enqueue the frame in the multicast TB_SOFQueue. Frames residing in the TB_SOF Queue are scheduled for forwardingby the EDS. The SDM builds the Prizma Cell Header and Interface deviceFrame header from information contained in the FCB. Cells from thisframe pass through Prizma and are reassembled into a frame on the downside of the CP's local blade. The SDM of the down side recognizes thatthe frame is a Guided Frame and signals the EDS to enqueue it in the GCQueue. This time when the GCH picocode analyzes the frame from the D_DS,the resp/ req field has a value of ‘1’b. This implies that this blade islocally attached to the CP and the Guided Frame is routed to the PortQueue corresponding to the CP. Frames from this queue are transmittedfrom Interface device back to the CP.

If, for any reason, the GCH picocode encounters a Guided Frame with theTB field of the Frame Control information equal to ‘0000’h, then the GCHpicocode interprets the frame as intended for only this blade and actaccordingly. This action is required during initialization when thevalue of the My_TB Register is ‘0000’h for all blades. The CP willinitialize the My_TB Register of the locally attached blade by sendingWrite Guided Command in a Guided Frame whose Frame Control Informationhas a TB value of ‘0000’h.

Any of the picoprocessors within the EPC can generate a Guided Frame.This frame can be the Unsolicited Guided Frame or any other form ofGuided Frame. Internally generated frames of this type are constructedin a way that does not allow acknowledgment (i.e. ack/ noack=‘0’b).These frames may be sent to one of the two picoprocessors (GCH or GTH)within the same EPC or to the GCH or GTH of some other blade.

Unsolicited Guided Frames may also be sent to the CP. Guided Framesdestined for the same EPC are constructed using data buffers in theD_DS. These frames are then enqueued in the GC or GT Queue forprocessing. These frames are then processed and discarded in the usualmanner. Unsolicited Guided Frames destined for the locally attached CPare constructed using data buffers in the D_DS. These frames areconstructed in a way that indicates that they have been executed by theEPC (i.e. resp/ req=‘1’b, and TB=My_TB). These frames are enqueued inthe Port Queue corresponding to the CP. Frames from this queue aretransmitted back to the CP.

Guided Frames destined for another blade can be constructed using databuffers in the D_DS or the U_DS. Unsolicited Guided Frames destined forthe CP are constructed in a way that indicates that they have beenexecuted by the EPC (i.e. resp/ req=‘1’b, and TB=My_TB). Framesconstructed using buffers from the D_DS are enqueued to the Wrap Port.These frames are moved to the U_DS and enqueued to the GC Queue on theup side. Unsolicited Guided Frames with a resp/req value of ‘1’b will berouted to the CP using TB value in the LAN_CP_Addr Register. Otherwise,the GCH picocode routes these frames using the TB value of the FrameControl Information of the Guided Frame. At the receiving blade, theframe is enqueued to the GC Queue of the down side. The GCH of thisblade executes and discard the frame (resp/ req=v0'b and gth/ gch=‘1’),or enqueues the frame to the GT Queue (resp/ req=‘0’b and gth/ gch=‘0’),or enqueues the frame to the Port Queue corresponding to the CP (resp/req=‘1’b). Frames constructed using data buffers in the U_DS areenqueued directly into the GC Queue of the up side. From this pointforward, these frames follow the same route and are handled in the sameway as those constructed using D_DS data Buffers. FIG. 5 shows thegeneralized format for guided frames.

The format shown is a logical representation with the most significantbyte on the left and the least significant byte on the right. Four bytewords begin with word 0 at the top and increase towards the bottom ofthe page.

Since Guided Frames must be routed and processed before the interfacedevice has been configured by the CP, these frames must be self-routing.The results normally obtained by look-up and classification arecontained in this Frame Control information field of the Guided Frameallowing the chip to update the FCB with this information withoutperforming a look-up operation. The target blade information containedin the Guided Frame is used by the Guided Frame Handler to prepare theLeaf Page field of the FCB. The CP provides the Target Blade informationwhile the GCH picocode fills in the other fields in the FCB. This FCBinformation is used by the SDM to prepare the Cell and Frame headers.The format of the Frame Control information field of the Guided Frame isshown in FIG. 6.

An explanation for the abbreviation at each bit position in FIG. 6follows:

-   resp/ req Response and Not Request indicator value. This field is    used to differentiate between request (unprocessed) and response    Guided Frames.

0 request

1 response

-   ack/ noack Acknowledgment or No Acknowledgment control value. This    field is use to control whether (ack) or not (noack) the GCH    picocode acknowledges the Guided Frame. Guided Frames that are not    to be acknowledged shall not contain any form of Guided Command that    performs a read.

0 No Acknowledgment

1 Acknowledgment

-   early/ late Early and Late Acknowledgment control value. This field    is used to control whether the acknowledgment requested (ack/    noack=‘1’b) occurs before (early) or after (late) the Guided Frame    has been processed. This field is ignored when ack/ noack=‘0’b.

0 Acknowledge after Guided Frame processing

1 Acknowledge before Guided Frame processing

-   neg/ all Negative Acknowledgment or Acknowledge All control value.    This field is ignored when the ack/ noack field has a value of ‘0’b    unless a guided command does not complete successfully.    -   0 Acknowledge all Guided Frames if ack/noack=‘1’b. Early or Late        Acknowledgment determined by value of early/late.    -   1 Acknowledge only Guided Frames that do not complete        successfully. This acknowledgment will occur independent of the        values of ack/ noack and early/ late and will of course be a        late acknowledgment.-   up/ down Up or Down control value. This value is used to control    whether the frame is processed on the up side or the down side. This    field is ignored when resp/req is ‘1’b. All multicast Guided Frames    shall have an up/down value of ‘0’b. In addition, Guided Commands    that require the use of GTH hardware assist instructions shall have    an up/down value of ‘0’b.

0 Down side processing

1 Up side processing

-   gth/ gch General Tree Handler or Guided Cell Handler control value.    This value is used to direct Guided Frames to the proper    picoprocessor.

0 GCH picoprocessor

1 GTH picoprocessor

-   TB Target Blade value. When resp/ req is ‘0’b, this field contains    routing information used by Prizma. Each bit position corresponds to    a Target Blade. If this value is ‘0000’h, then the Guided Frame is    assumed to be for this blade and is executed accordingly. A value of    ‘1’b in one or more bit positions of the TB field indicates that the    cell is routed to the corresponding Target Blade(s). When resp/ req    is ‘1’b, the field contains the My_TB value of the responding blade.

Word 1 of the Guided Frame contains a correlator value (FIG. 7). Thisvalue is assigned by the CP software to correlate Guided Frame responseswith their requests. The Correlator includes a plurality of bits withassigned functions.

Every Guided Command begins with a Command Control Information field.This Command Control contains information that aids the GCH picocode inprocessing a Guided Frame. The format for this information is shown inFIG. 8.

Length value: This value indicates the total number of 32 bit wordscontained in the Control Information (Cmd Word 0), The AddressInformation (Cmd Word 1), and Operand (Cmd Words 2+) portions of theGuided Frame.

Completion Code value: This field is initialized by the CP and ismodified by the GCH picocode when processing Guided Commands. The GCHpicocode uses this field for completion status for the preceding GuidedCommand in the command list. Since all Guided Command lists terminatewith the End Delimiter Guided Command, the completion status of the lastcommand is contained in the End Delimiter's Completion Code field.

Guided Command Type Value (Symbolic Name)

Type Symbolic Name Value Type Description End_Delimiter 0000 mark theend of a Guided Frame sequence Build_TSE_Free_List 0001 build a freelist. Software_Action 0010 execute software action Unsolicited 0011frames initiated by the EPC picocode Block_Write 0100 write a block ofdata to consecutive addresses Duplicate_Write 0101 write duplicate datato registers or memory. Read 0110 request and respond for readingregister or memory data 0111 reserved Insert_Leaf 1000 insert a leafinto the search tree. Update_Leaf 1001 update a leaf of the search treeRead_Leaf 1010 request and respond for reading of Leaf Page data 1011reserved Delete_Leaf 1100 delete a leaf of the search tree 1101-1111reserved

The addressing information contained in the Guided Frame identifies anelement within the Networking Processor's addressing scheme. The generalform for the Address Information field is shown in FIG. 9.

The Interface device employs a 32 bit addressing scheme. This addressingscheme assigns an address value to every accessible structure of theInterface device. These structures are either internal to the Processoror connected to interfaces under the control of the Processor. Some ofthese structures are accessed by the Embedded Processor Complex (EPC)via an internal interface called the Web Interface. The remainder of thestructures are accessed via memory controller interfaces. In all casesthe general form of the address is shown in FIG. 10.

The Network Controller is subdivided into major chip islands. Eachisland is given a unique Island ID value. This 5 bit Island ID valueforms the 5 most significant bits of the address for structurescontrolled by that chip island. The correspondence between encodedIsland ID value and the chip island name is shown in FIG. 11. The secondportion of the Web address consists of the next most significant 23bits. This address field is segmented into a structure address portionand an element address portion. The number of bits used for each segmentmay vary from island to island. Some islands may contain only a fewlarge structures while others may contain many small structures. Forthat reason there is no fixed size for these address segments. Thestructure address portion is used to address an array within the islandwhile the element address portion is used to address an element withinthe array. The remaining portion of the address is to accommodate theWeb Interface's 32 bit data bus limitation. This 4 bit word address isused for selecting 32 bit segments of the addressed element. This isnecessary for moving structure elements wider than 32 bits across theNetwork Controller's Web Data Bus. Word address value ‘0’h refers to the32 most significant bits of the structure element while sequential wordaddress values correspond to successively less significant segments ofthe structure element. The word address portion of the address is notrequired for structures not accessed via the Web Interface. For thisreason, the Up Data Store, Control Memories, and Down Data Store makeuse of the entire 27 least significant bits of address to accessstructure elements. Another exception to this format is the address forthe SPM Interface. In that case all 27 bits of address are used and noelement is greater than 32 bits in width.

The Embedded Processing Complex (EPC) provides and controls theprogrammability of the Interface device Chip. It includes the followingcomponents (see also FIG. 12A):

N processing units, called GxH: The GxHs concurrently execute picocodethat is stored in a common Instruction Memory. Each GxH consist of aProcessing Unit core, called CLP, which contains a 3-stage pipeline, 16GPRs and an ALU. Each GxH also contains several coprocessors, like forexample the Tree Search Engine.

Instruction Memory: Is loaded during initialization and contain thepico-code for forwarding frames and managing the system.

A Dispatcher: Dequeues frame-addresses from the up and down dispatcherqueues. After dequeue, the dispatcher pre-fetches part of theframe-header from the up or down DataStore (DS) and stores this in aninternal memory. As soon as a GxH becomes idle, the Dispatcher passesthe frame header with appropriate control information, like the CodeInstruction Address (CIA) to the GxH. The dispatcher also handles timersand interrupts.

A Tree Search Memory (TSM) Arbiter: There are a number of sharedinternal and external memory locations available to each GxH. Since thismemory is shared an arbiter is used to control access to the memory. TheTSM can be accessed directly by the picocode, which can for example beused to store aging tables in the TSM. Also, the TSM will be accessed bythe TSE during tree searches.

The Completion Unit (CU): The Completion Unit performs two functions.First, it interfaces the N Processing Units to the UP and Dn EDS(Enqueue, Dequeue and Schedule Island). The EDS performs the enqueueaction: a frame address, together with appropriate parameters called theFCBPage, is queued in either a transmission queue, a discard queue, or adispatcher queue. Second, the Completion Unit guarantees frame sequence.Since it may happen that multiple GxHs are processing frames that belongto same flow, precautions must be taken that these frames are enqueuedin the up or dn transmission queues in the right order. The CompletionUnit uses a label that is generated by the Classifier Hardware Assistupon frame dispatch.

Classifier Hardware Assist: For up-frames, the Classifier HardwareAssist provides a classification for well known cases of frame formats.Classification results are passed to the GxH, during frame dispatch, interms of the CIA and contents of one or more registers. For dn-frames,the Classifier Hardware Assist determines the CIA, depending on theframe header. For both up and dn frame dispatches, the ClassifierHardware Assist generates a label that is used by the Completion Unit tomaintain frame sequence.

Up and dn DataStore Interface and arbiter: Each GxH has access to the upand dn DataStore: read access is provided when reading “more Fish” andwrite access is provided when writing back the contents of the FishPoolto the DataStore. Since there are N Processing Units, and only one ofthem at a time can access the up DataStore and one at a time can accessthe dn DataStore, one arbiter for each DataStore is required.

WEB Arbiter and WEBWatch interface: The WEB Arbiter arbitrates among theGxHs for access to the WEB. All GxHs have access to the WEB which allowsaccess all memory and registers functions in an Interface device. Thisallows any GxH to modify or read all configuration areas. The WEB can bethought of as the Interface device memory map. The WEBWatch interface,provides access to the entire WEB from outside the chip using 3 chip-IOpins.

Debug, Interrupts and Single Step Control: The WEB allows the GCH orWEBWatch to control each GxH on the chip when necessary. For example,the WEB can be used by the GCH or WEBWatch to single step instructionson a GxH.

An embedded general purpose processor, like a PowerPC.

There are four types of GxH (FIG. 12B):

GDH (General Data Handler). There are eight GDHs. Each GDH has a fullCLP with the five coprocessors (which are described in the nextsection). The GDHs are mainly used for forwarding frames.

GCH (Guided Cell Handler). The GCH has exactly the same hardware as aGDH. However, a guided frame can only be processed by the GCH. It isprogrammable on the WEB (CLP_Ena register) if the GCH is enabled to alsoprocess dataframes (in which case it takes the role of a GDH). The GCHhas additional hardware compared to the GDH: hardware assist to performtree inserts and deletes. The GCH is used to execute guided-cell relatedpicocode, perform chip and tree management related picocode like agingand to exchange control information with the CP and/or another GCH. Whenthere is no such task to perform the GCH will execute frame forwardingrelated picocode, and in this case behaves exactly like a GDH.

GTH (General Tree Handler). The GTH has additional hardware assist toperform tree inserts, tree deletes and rope management. The GTH willprocess dataframes when there are no frames (containing tree managementcommands) in the GPQ. GPH (General Power PC Handler). The GPH hasadditional hardware compared with the GDH and GTH. The GPH interfaces tothe General Purpose Processor by means of the Mailbox interface (i/f).

The number of GxHs (ten) is a “best-guess”. Performance evaluation willdetermine how much GxH are really required. The architecture andstructure is completely scaleable towards more GxH and the onlylimitation is the amount of silicon area (which should then also includea larger arbiter and instruction memory).

Each GxH is structured as shown in FIG. 12C. In addition to the CLP withGeneral Purpose Registers (GPR) and Arithmetic Logic Unit (ALU), eachGxH contains the following five coprocessors:

(DS) Coprocessor Interface. Interfaces to the Dispatcher and to thesub-islands that provide read and write access to the up and dnDataStores. The DS Interface contains the so called FishPool.

The Tree Search Engine Coprocessor (TSE). The TSE performs searches inthe trees, and also interfaces to the Tree Search Memory (TSM).

Enqueue Coprocessor. Interfaces the Completion Unit Interface andcontains the FCBPage. This Coprocessor contains a 256-bit register withadditional hardware assist that the picocode must use to build theFCBPage, which contain the enqueue parameters. Once the FCBPage isbuilt, the picoprocessor can execute an enqueue instruction, whichcauses this coprocessor to forward the FCBPage to the Completion Unit.

WEB InterfaceCoprocessor. This coprocessor provides an interface to theWEB Arbiter and allows reading and writing to/from the Interface deviceWEB.

Checksum Coprocessor. Generates checksums on frames stored in theFishpool (described hereinafter).

The Processing Units are shared between ingress processing and egressprocessing. It is programmable how much bandwidth is reserved foringress processing versus egress processing. In the currentimplementation, there are two modes: 50/50 (i.e. ingress and egress getthe same bandwidth) or 66/34 (i.e. ingress gets twice as much bandwidthas egress).

Operation of the Processing Units is event-driven. That is, framearrival is treated as an event, as well as popping of a timer or aninterrupt. The dispatcher treats different events in an identicalfashion, though there is a priority (first interrupt, then timer-eventsand finally frame arrival events). When an event is handed to aProcessing Unit, appropriate information is given to the ProcessingUnit. For frame arrival events, this includes part of the frame header,and information coming from the hardware classifier. For timer andinterrupts, this includes the code entry point and other informationthat relates to the event.

When a frame arrives on the ingress side, and the number of receivedbytes of this frame has exceeded a programmable threshold, the addressof the frame-control-block is written in a GQ.

When a complete frame has been re-assembled on the egress side, theframe address is written in a GQ. There are four types of GQ's (and foreach type, FIG. 12B, there is an ingress version and a egress version):

GCQ: contains frames that must be processed by the GCH.

GTQ: contains frames that must be processed by the GTH.

GPQ: contains frames that must be processed by the GPH.

GDQ: contains frames that can be processed by any GDH (or GCH/GTH whenthey are enabled to process dataframes). For the GDQ, there are multiplepriorities, whereby frames enqueued in a higher priority GDQ will beprocessed before frames enqueued in a lower priority queue.

Some Processing Units may be specialized. In the current implementation,there are four types of Processing Units (GxH) (see also FIG. 12B):

GDH (General Data Handler). The GDHs are mainly used for forwardingframes.

GCH (Guided Cell Handler). The GCH has exactly the same hardware as GDH.However, a guided frame can only be processed by the GCH. It isprogrammable on the WEB (CLP_Ena register) if the GCH is enabled to alsoprocess dataframes (in which case it takes the role of a GDH).

GTH (General Tree Handler). The GTH has additional hardware compared tothe GDH/GCH: hardware assist to perform tree inserts, tree deletes andrope management. The GTH will process dataframes when there are noframes (containing tree management commands) in the GPQ.

GPH (General PowerPC Handler). The GPH has additional hardware comparedto the GDH/GTH. The GPH interfaces to the embedded PowerPC by means of amail-box interface.

In an actual implementation, the role of GCH, GTH and GPH can beimplemented on a single Processing Unit. For example one implementationcould have one Processing Unit for GCH and GPH. A similar comment holdsfor the GCQ, GTQ and GPQ.

The purpose of the Datastore Coprocessor is:

To interface to the Up DataStore, which contains frames that have beenreceived from the media, and the Down DataStore, which containsreassembled frames received from the Prizma Atlantic Switch System.

The Datastore Coprocessor also receives configuration information duringthe dispatch of a timer event or interrupt.

The Datastore Coprocessor is able to calculate checksums on frames.

The Datastore Coprocessor contains a FishPool (that can hold 8 fish), ascratch memory (that can hold 8 fish) and some control registers toread/write FishPool contents from/to the up or down datastore. TheFishPool can be seen as some kind of work area for the Datastore:instead of reading/writing directly to a Datastore, a larger amount offrame data is read from the Datastore into the Fishpool or a largeramount of data is written from the Fishpool into the Datastore. The unitof transfer is a Fish, which equals 16 Bytes.

The Fishpool can be seen as a memory that can contain 8 fish, that is 8words of 128 bit each. In the CLP processor architecture, the Fishpoolis a register array of 128 bytes. Each byte in the Fishpool has a 7-bitbyte address (0 . . . 127) and access is on a 16-bit or 32-bit basis.Like all register arrays, the Fishpool has a circular addressing scheme.That is, addressing a word (i.e. four bytes) starting at location 126 inthe Fishpool returns bytes 126, 127, 0 and 1. Furthermore, from aDatastore Coprocessor point of view, fish-locations in the Fishpool havea 3-bit fish-address.

Upon frame dispatch the first N fish of a frame are automatically copiedin the Fishpool by the Dispatcher. The value of N is programmable in thePortConfigMemory. Typically, N equals four for up frame dispatch, 2 fordn unicast frame dispatch, 4 for dn multicast frame dispatch and 0 forinterrupts and timers.

The picocode can read more bytes from a frame, in which case theDatastore Coprocessor automatically reads the frame data into thefishpool at the next fish address, wrapping automatically to 0 when theboundary of the Fishpool has been reached. Also, the picocode can reador write the up/down datastore at an absolute address.

The WEB Coprocessor interfaces to the EPC WEB Arbiter. The EPC WEBArbiter Arbitrates among the ten GxH and the WEB Watch to become amaster on the Interface device WEB interface. This allows all GxH toread and write on the WEB.

The interface device memory complex provides storage facilities for theEmbedded Processing Complex (EPC) FIG. 12A. The memory complex includesthe Tree-Search Memory (TSM) Arbiter and a plurality of on-chip andoff-chip memories. The memories store tree structures, counters andanything else that the pico code requires memory access for.Furthermore, the memories are used to store data structures that areused by the hardware, like free lists, queue-control-blocks, etc. Anymemory location which is not allocated for trees or which is notallocated for trees or which is not used by the hardware is by defaultavailable for pico code use, like counters and aging tables.

FIG. 13 shows a more detailed block diagram of the memory complex. Thetree-search memory (TSM) arbiter provides the communication link betweenthe Embedded Processors (GxH) and the memories. The memories include 5on-chip SRAMs, 1 off-chip SRAM, and 7 off-chip DRAMS. The TSM Arbiterincludes ten Request Control Units (each one connected to one of theEmbedded Processor GxH) and 13 memory arbiter units, one for eachmemory. A bus structure interconnects the Request Control Units and thearbiter units in such a way that each control unit and its connected GxHhave access to all memories.

The control unit includes necessary hardware to steer data between theEmbedded Processor (GxH) and the arbiters.

The SRAM arbiter units, among other things, manage the flow of databetween the Embedded Processor GxH and the on-chip and off-chip SRAMs.

The DRAM Arbiter Units, among other things, manages the flow of databetween the Embedded Processor (GxH) and the off-chip DRAM devices.

Each Memory Arbiter contains a “back-door” access, which is typicallyused by other parts of the chip and has highest access priority.

The DRAM Memories can run in two modes of operation:

-   -   TDM-mode. Memory access to the four banks in the DDRAM is done        alternating read-“windows” and write-windows, whereby in a read        window, access to any of the four banks is read-only and in a        write window, access to any of the four banks is write only.        Using TDM-mode for multiple DDRAMs allows sharing some control        signals between the DDRAMs and hence this saves some chip IOs        (which is a very scarce resource).    -   Non-TDM-mode. Memory access to the four banks in the DDRAM can        be a combination of read and write which must follow some rules.        For example, one can do a read in bank A and a write in bank C        within an access window.    -   The TSM Arbiter allows N Requesters simultaneous access to M        memories. When multiple Requesters want to access the same        memory, a round-robin arbitration is performed.    -   The M memories can have different properties. In our current        implementation, there are three memory types: internal SRAM,        external SRAM and external DDRAM.    -   The M memories and N Requesters are homogeneous: any Requester        can access any memory.    -   Some memories are logically divided into multiple sub-memories        (like four banks in the DDRAM), which can be logically accessed        simultaneously.    -   Part of the M memories are used for control memories containing        internally used data structures, which have a high priority        access compared to the picoprocessors. This also allows        debugging of the chip, since the picoprocessors can read the        contents of the control memories.    -   The arbiter supports read access, write access and        read-add-write, whereby an N-bit integer is added to the        contents of the memory in an atomic operation.    -   A general address scheme is used to access the M memories, such        that the physical location of an object in the memory is        transparent.

The concept of trees as used by the Tree Search Engine to store andretrieve information. Retrieval, i.e., tree-searches and also insertsand deletes are done based on a Key, which is a bit-pattern like, forexample, a MAC source address, or the concatenation of an IP sourceaddress and IP destination address. Information is stored in a controlblock called Leaf, which contains at least the Key (as will be seenlater, the stored bit pattern is actually the hashed Key). A leaf canalso contain additional information, like aging information, or userinformation, which can for example be forwarding information like targetblade and target port numbers.

There are tree types (FM, LPM and SMT) and associated tree typesearches, namely: fixed match, software managed tree and largest prefixmatch. An optional additional criterium for checking the leaf during atree search is the VectorMask. Roping, aging and a latch are used toincrease search performance.

The search algorithm for FM trees is shown in FIG. 14. The searchalgorithm operates on input parameters, which include the Key, performsa hash on the Key, accesses a Direct Table (DT), walks the tree throughPattern Search Control Blocks (PSCBs) and ends up at a Leaf (FIG. 14).There are three types of trees, each with its own search algorithm,which causes the tree-walk to occur according to different rules. Forexample, for Fixed Match (FM) trees, the datastructure is a PatriciaTree. When a Leaf has been found, this Leaf is the only possiblecandidate that can match the input Key. For Software Managed Trees,there can be multiple Leafs that are chained in a linked list. In thiscase, all Leafs in the chain are checked with the input Key, until amatch has been found or until the chain has been exhausted. A so-called“compare at the end” operation, which compares the input Key with thepattern stored in the Leaf, verifies if the Leaf really matches theinput Key. The result of the search will be OK when the Leaf has beenfound and a match has occurred, or KO in all other cases.

The input to a search operation consists of the following parameters:

Key (128 bits). The Key must be built using special picocodeinstructions prior to the search (or insert/delete). There is only oneKey register. However, after the tree search has started, the Keyregister can be used by the picocode to build the key for the nextsearch, concurrently with the TSE performing the search. This is becausethe TSE bashes the Key and stores the result in an internal HashedKeyregister (thus, in reality, there are 2 Key registers). KeyLength (7bits). This register contains the length of the Key in bits. It isautomatically updated by hardware during building of the Key. LUDefIndex(8 bits). This is an index into the LUDefTable, which contains a fulldefinition of the tree in which the search occurs. The LUDefTable isdescribed in detail later. TSRNr (1 bit). The search results can bestored either in Tree Search Result Area 0 (TSR0) or TSR1. This isspecified by TSRNr. While the TSE is searching, the picocode can accessthe other TSR to analyze the results of a previous search. VectorIndex(6 bits). For trees which have the VectorMask enabled (which isspecified in the LUDefTable), the VectorIndex denotes a bit in theVectorMask. At the end of the search, the value of this bit is returnedand can be used by picocode.

The input Key will be hashed into a HashedKey, as shown in FIG. 14.There are six fixed hash algorithms available (one “algorithm” performsno hash function). It is specified in the LUDefTable which algorithmwill be used. A programmable hash function may be used to addflexibility.

The output of the hash function is always a 128-bit number, which hasthe property that there is a one-to-one correspondence between theoriginal input Key and the output of the hash function. As will beexplained below, this property minimizes the depth of the tree thatstarts after the Direct Table.

If colors are enabled for the tree, which is the case in the example ofFIG. 14, the 16-bit color register is inserted in the 128-bit hashfunction output. The insertion occurs directly after the Direct Table.I.e., if the Direct Table contains 2^(N) entries, then the 16-bit colorvalue is inserted at bit position N, as shown in the figure. The outputof the hash function, together with the inserted color value (whenenabled), is stored in the HashedKey register.

The hash function is defined such that most entropy in its outputresides in the highest bits. The N highest bits of the HashedKeyregister are used to calculate an index into the Direct Table (DT).

The search starts with an access into the Direct Table: a DTEntry isread from the direct table. The address used to read the DTEntry iscalculated from the N highest bits of the HashedKey, as well as ontree-properties as defined in the LUDefTable. This is explained indetail below. The DTEntry can be seen as the root of a tree. Theparticular tree datastructure that is used depends on the tree-type. Atthis point it suffices to say that a Patricia Tree datastructure is usedfor FM trees, and extensions to Patricia Trees for LPM and SMT trees.

An example of the use of an 8 entry DT is shown in FIG. 15. It can beseen that the search time (i.e., the number of PSCBs that must beaccessed) can be reduced by using a DT. Thus, by increasing the DT size,a trade-off can be made between memory usage and search performance.

As can be seen from FIG. 15, a DTEntry can contain the followinginformation:

-   -   Empty. There are no Leafs attached to this DTEntry.    -   A pointer to a Leaf. There is a single Leaf attached to this        DTEntry.    -   A pointer to a PSCB. There are more than one Leafs attached to        this    -   DTEntry. The DTEntry defines the root of a tree.

The Search Algorithm for a software managed tree and algorithm forgenerating the tree is set forth in U.S. patent application Ser. No.09/312,148 and is incorporated herein by reference.

An algorithm termed “Choice Bit Algorithm” uses a certain metric tobuild a binary search tree based upon bits selected from items termed“rules” in a set or universe of rules. All our examples are couched interms of Internet Protocol (IP) headers, but a fixed format header ofany type could be used instead.

In IP, each Rule pertains to certain Keys which might be built with thefollowing subsections: Source Address (SA), Destination Address (DA),Source Port (SP), Destination Port (DP), and Protocol (P). These dataare respectively 32, 32, 16, 16, and 8 bits long and so a Key to betested consists of 104 bits. The Choice Bit Algorithm finds certain ofthe 104 bits which are especially useful. Testing the few bits in effecteliminates all but one or all but a few rules from possible application.For some rules, testing inequalities by means of simple compareoperations are also appropriate. The bit tests and compares arelogically organized in a binary tree. The tree is mapped into a hardwareenabled structure that tests bits at high speeds. Such testing resultsin just one rule or a small number of rules (called a leaf chain) whichthe Key might fit. In the former case, the Key is then tested in full bythe rule. In the latter case, the Key is then tested in a lattice oftests using compares and full rule tests.

Each rule in the rule set is associated with an action which is taken ifthe rule is the highest priority rule which fits the key. Rules canintersect (one key fits two or more rules). In that case, rules can begiven priority numbers 1, 2, 3, . . . , so that any two intersectingrules have different priorities (an administrator must declare whichrule dominates if a key fits two or more). Thus if more than one ruleremains to be tested after the bit tests and compares, the rules aretested in order of priority. A lower priority number designates a rulewith higher priority.

If no fit is found at all, some default provision may be specified.

The search algorithm for the longest Prefix Matching method is set forthin U.S. Pat. No. 5,787,430, incorporated herein by reference. The methodrequires entering at a node of said database (root node); determining asearch path from one node to another through said tree-like database bysuccessively processing segments of said search argument which compriseonly those parts of the entries which are necessary to identify the next(child) node, and said second link information until said segments areconsumed or a (leaf) node lacking said second link information isreached; comparing with said search argument an entry stored in the nodeat which said search path ended; and if no at least partial matchbetween the search argument and said entry is found in said currentnode, backtracking said search path by processing said first linkinformation of said current node; and repeating the previous two stepsuntil said at least partial match is found or said root node is reached.

FIG. 16 shows an embodiment of the main switching fabric device.Preferably, each interface device chip (called Rainier) has at least twointegrated parallel-to-serial systems (DASL) which receive parallel dataand convert the data to a high speed serial data stream which isforwarded over a serial link to the switching fabric device. Datareceived from switching fabric device on a high speed serial link isconverted to parallel data by another DASL. An embodiment of theSerializer/Deserializer termed Data Align Serial Link (DASL) isdescribed herein.

At least one DASL interfaces the switching fabric device to the seriallinks. Data from the serial link is converted into parallel data whichis delivered to switching fabric device. Likewise, parallel data fromswitching fabric device is converted to serial data which is deliveredto the serial links. The serial links can be aggregated to increasethroughput.

Still referring to FIG. 16, the switching system includes switch fabric11, input switch adapters 13 (13-I . . . 13-k) which are connected tothe switch fabric input ports 15 (15-I . . . 15-k), and output switchadapters 17 (17-I . . . 17-p) which are connected to the switch fabricat output ports 19 (19-I . . . 19-p).

Incoming and outgoing transmission links 21 (21-I . . . 21-q) and 23(23-I . . . 23-r) are connected to the switch system by line (link)adapters 25 (25-I . . . 25-q) and 27 (27-I . . . 27-r), respectively.The transmission links carry circuit switched or packet switched trafficfrom and to attached units such as work stations, telephone sets or thelike (links designated WS), from and to local area networks (linksdesignated LAN), from or to Integrated Services Digital Networkfacilities (links designated ISDN), or from and to any othercommunication systems. Furthermore, processors may be attached directlyto switch adapters 13 and 17. The line adapters (LA) and switch adapters(SA) have a common interface.

At the input switch adapters, various services from packet switched andcircuit switched interfaces are collected and converted into uniformminipackets (having one of several possible fixed lengths), with aheader containing routing information designating the required outputport (and outgoing link) of the switch. Some details on the minipacketformat and on minipacket generation in the input switch adapters and ondepacketization in the output switch adapters will be given in the nextsections.

The switch fabric routes the minipackets via a fast self-routinginterconnection network from any input port to any output port. Thestructure of the self-routing network is such that minipackets can berouted simultaneously internally without any conflicts.

The heart of the switching system is the switch fabric. Two differentimplementations are considered and will be described separately. In oneimplementation, the switch fabric comprises a self-routing binary treefor each input port, connecting the respective input port to all outputports; the switch fabric comprises k such trees in combination (if kinput ports are provided). In the other implementation, a bus structureWith an Output Ram is Provided as a Slice for Each Output Port,Connecting all Input Ports to the respective output port; the switchfabric comprises p such slices in combination (if p output ports areprovided).

DASL is described in U.S. application Ser. No. 09/330,968, filed 11 Jun.1999 and incorporated herein by reference. The DASL Interface receivesdata from a parallel interface such as a CMOS ASIC, partitions the bitsfrom the parallel interface into a smaller number of parallel bitstreams. The smaller number of parallel bit streams are then convertedinto a high speed serial stream, which is transported via a transmissionmedium to the receiver of the other module. A differential driver withcontrol impedance drives the serial bit stream of data into thetransmission media.

DASL implements the method of parsing a data stream presented as N bitsin parallel into a plurality of portions each having n bits, wherein nis a fraction of N; serializing each n bit portion of the data stream;transferring each serialized portion over a corresponding one of aplurality of parallel channels; and deserializing each transferredportion of the data stream to restore the data stream to presentation asN bits in parallel.

In the drawings and specifications there have been set forth preferredembodiments of the inventions here disclosed and, although specificterms are used, the description thus given uses terminology in a genericand descriptive sense only and not for purposes of limitation.

1. An apparatus for transporting control information in a communicationssystem, said apparatus comprising: a network processor; a control pointprocessor operatively coupled to said network processor; and a guidedframe generated by said control point processor, wherein said guidedframe comprises: a first section in which frame control information isplaced and is used by said network processor to update at least onecontrol register within said network processor; a second sectioncarrying correlators assigned by said control point processor tocorrelate guided frame responses with their requests; a third sectioncarrying one or a sequence of guided commands; and an End delimiterguided command.
 2. The apparatus of claim 1, wherein said control pointprocessor generates routing information and encapsulates said guidedframe with said routing information.
 3. The apparatus of claim 2,wherein said routing information comprises: a code identifying aparticular frame type; a source address; and a destination address. 4.The apparatus of claim 1, wherein said first, second, and third sectionsare arranged in sequential order.
 5. The apparatus of claim 1, whereinsaid first section comprises: a first word having a first field with aset of control bits and a second field with target blade information;and a second word having a reserved field, a source port field withsource port information, and a source blade field with source bladeinformation.
 6. The apparatus of claim 1, wherein said second sectioncomprises a word having a reserved field, a length field concatenated tosaid reserved field, and at least one correlator word following saidlength field.
 7. The apparatus of claim 1, wherein each guided commandin said third section comprises: a first command word in which commandcontrol information is carried, said first command word comprising alength field indicating a total number of 32-bit words contained in saidcommand control information, a completion code field to carryinformation regarding status of preceding guided commands, and a guidedframe type field carrying a code indicating one of a plurality ofcommands; and a second command word with an address field used toidentify an element within said network processor.
 8. The apparatus ofclaim 1, wherein said control point processor comprises a softwaredriver.